Catalog of Structural Database Refactorings

www.agiledata.org: Techniques for Successful Evolutionary/Agile Database Development

A structural database refactoring changes the structure of a table, column or view so as to improve your database design without changing its semantics.

Refactoring	Example
Drop Column. Remove a column from an existing table.
Drop Table. Remove an existing table from the database.
Drop View. Remove an existing view.
Introduce Calculated Column. Introduce a new column based on calculations involving data in one or more tables.
Introduce Surrogate Key. Replace an existing natural key with a surrogate key.
Merge Columns. Merge two or more columns within a single table.
Merge Tables. Merge two or more tables into a single table.
Move Column. Migrate a table column, with all of its data, to another existing table.
Rename Column. Rename an existing table column with a name that explains the purpose.
Rename Table. Rename an existing table with a name that explains the purpose.
Rename Table (via a view). Rename an existing table with a name that explains its purpose.
Rename View. Rename an existing view with a name that explains the purpose.
Replace Column. Replace an existing non key column with a new one.
Replace LOB With Table. Replace a large object (LOB) column which contains structured data with a new table or in the same table.
Replace One-to-Many With Associative Table. Replace a one-to-many association between two tables with an associative table.
Replace Surrogate Key With Natural Key. Replace a surrogate key with an existing natural key.
Split Column. Split a column into one or more columns within a single table.
Split Table. Vertically split (e.g. by columns) an existing table into one or more tables.

Recommended Books

This book describes, in detail, how to refactor a database schema to improve its design. The first section of the book overviews the fundamentals evolutionary database techniques in general and of database refactoring in detail. More importantly it presents strategies for implementing and deploying database refactorings, in the context of both "simple" single application databases and in "complex" multi-application databases. The second section, the majority of the book, is a database refactoring reference catalog. It describes over 60 database refactorings, presenting data models overviewing each refactoring and the code to implement it.

Working Effectively With Legacy Code describes techniques for refactoring and testing existing, legacy code. Few teams have the luxury of building everything from scratch, instead they must work from an existing base of code, or minimally integrate with other legacy systems. In this book Michael Feathers covers the fundamental techniques which agile developers need to effectively work in these sorts of environments. You don’t need to stop all development and rework your legacy code, instead you can ease into it over time, and this book shows you how to do that successfully.

References and Suggested Online Readings

Agile/Evolutionary Data Modeling
Agile Database Best Practices
Catalog of Database Refactorings
Current State of Data Management: July 2006 Survey Results
Database Refactoring Smells
Database Regression Testing
On Relational Theory
The Process of Database Refactoring
Refactoring Databases (Objectview Issue #10, 3.4 Meg PDF)
The Rename Column Database Refactoring: A Complete Example
Ruby on Rails -- Active Record Migration
Sundog Database Refactoring Tool
Visual Studio Team Edition for Database Professionals
Whence Data Management? explores the current state of database management, including database refactoring
Whence Data Quality? explores the current state of data quality

This book describes the philosophies and skills required for developers and database administrators to work together effectively on project teams following evolutionary software processes such as Extreme Programming (XP), the Rational Unified Process (RUP), the Agile Unified Process (AUP), Feature Driven Development (FDD), Dynamic System Development Method (DSDM), or The Enterprise Unified Process (EUP). In March 2004 it won a Jolt Productivity award.

This book presents a full-lifecycle, agile model driven development (AMDD) approach to software development. It is one of the few books which covers both object-oriented and data-oriented development in a comprehensive and coherent manner. Techniques the book covers include Agile Modeling (AM), Full Lifecycle Object-Oriented Testing (FLOOT), over 30 modeling techniques, agile database techniques, refactoring, and test driven development (TDD). If you want to gain the skills required to build mission-critical applications in an agile manner, this is the book for you.

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